1. Field of the Invention
The present invention relates to a projection system and information processing apparatus.
2. Description of the Related Art
Conventionally, a projector that projects an image generated by a light valve such as a liquid crystal panel onto a screen has been known as a projection apparatus. Recently, the resolution of images has been increased, and demands have arisen for displaying an image having a large number of pixels such as 4K2K or 8K4K onto a large screen. To increase the number of pixels of a projector or increase the screen size, it is generally necessary to downsize a light valve such as a liquid crystal panel or use a high-luminance light source, so the cost increases. Therefore, an image having a large number of pixels is often displayed on a large screen by multi projection using a plurality of inexpensive projectors each including an ordinary light valve or an ordinary light source.
Multi projection is a method of displaying one image as a whole by connecting a plurality of projected images. Note that one projected image (or projection screen) obtained by connecting a plurality of projected images (or projection screens) will be called “an integrated image (or integrated projection screen)” hereinafter for the sake of convenience. If a plurality of projected images are not strictly aligned when they are connected, joints are seen in an integrated image, and the image quality deteriorates. Accordingly, a process called edge blend that makes joints inconspicuous is performed. Edge blend is a process by which a plurality of projected images are partially superposed, and the superposed portion of each projected image is darkened such that the illuminance of the superposed portion is equal to that of an unsuperposed portion when the illuminances of the projected images are summed.
A practical example of edge blend will be explained with reference to FIGS. 1A to 1C. This is an example in which two projected images are connected in the horizontal direction by using two projectors. FIG. 1A shows a left projected image including two regions, that is, an unsuperposed region A and superposed region AR. FIG. 1C shows the darkening process of edge blend. Referring to FIG. 1C, the horizontal direction of a projected image is the abscissa, and the ordinate represents the gain to an image in that position. The solid line in FIG. 1C is the gain to the left projected image. The gain is 100% in the unsuperposed region A, but gradually decreases to 0% (darkens) toward the image edge in the superposed region AR. On the other hand, FIG. 1B shows a right projected image including two regions, that is, an unsuperposed region B and superposed region BL. The alternate long and short dashed line in FIG. 1C is the gain to the right projected image. Similar to the gain on the left side, the gain is 100% in the unsuperposed region B, but gradually decreases to 0% (darkens) toward the image edge in the superposed region BL.
In the edge blend process, the total gain of the regions AR and BL is set at 100% when the two regions are superposed. The dotted line in FIG. 1C indicates the total gain. Thus, an integrated image is formed by three regions, that is, the region A, the superposed region of the regions AR and BL, and the region B, and a large image having a large number of pixels is projected by inputting corresponding partial images to two projectors. In addition, the gain gradually changes in the peripheries of the superposed regions AR and BL. Even when a slight misalignment occurs in the projected image, therefore, the joint hardly becomes conspicuous. Although edge blend is performed by horizontally arranging two images in this example, it is naturally possible to arrange three or more images. In this case, projectors on the right and left ends perform the same processing as shown in FIGS. 1A to 1C, and another projector performs processing as shown in FIG. 1A or 1B on the right and left edges of one image. It is also possible to arrange images in the vertical direction, instead of the horizontal direction. In this case, the edge blend process as shown in FIGS. 1A to 1C is performed on the upper and lower edges in an image. Furthermore, when implementing multi projection by arranging a plurality of projectors in the vertical and horizontal directions, like 2×2 or 3×3, the edge blend process need only be performed on the upper and lower edges and right and left edges in an image.
A technique of projecting an image by performing the above-mentioned edge blend is described in, for example, Japanese Patent Laid-Open No. 2010-134396. Japanese Patent Laid-Open No. 2010-134396 describes a technique by which a PC generates a synthetic image by generating and adding an edge blended portion to an input image from a source device, transmits the synthetic image to projectors, and each projector cuts out a corresponding portion from the synthetic image and displays the partial image.
A projector using a light valve having a pixel structure desirably displays an input image from a source device without performing any scaling (resolution conversion), in order to improve the image quality. This is so because if scaling is performed, demerits of the image quality occur, for example, moire occurs, an information amount decreases, and high-frequency components are lost. To form an image on the entire surface of a light valve in order to display a large image, therefore, the number of pixels of an input image and that of the light valve are preferably equal.
On the other hand, when using a projector that performs edge blend, the size of a superposed region must be changeable by the user for the following reason. That is, when projected images can strictly be aligned, a large image can be displayed by downsizing or eliminating a superposed region. If strict alignment is difficult, however, it is necessary to enlarge a superposed region to make misalignment difficult to see. Accordingly, if the size of a superposed region is changeable when performing edge blend, the image quality often deteriorates because the number of pixels of an input image from a source device does not match that of an integrated image.
In above-mentioned Japanese Patent Laid-Open No. 2010-134396, when generating a synthetic image by generating and adding an edge blended portion to an input image from a source device, the resolution of the synthetic image is set to be an integral multiple of the resolution of a plurality of projectors as transmission sources. However, the deterioration of the image quality described above cannot be suppressed because the number of pixels (the resolution) of an input image from a source device is not taken into consideration. That is, depending on the number of pixels (the resolution) of an input image, scaling must be performed when generating an integrated image, and the image quality may deteriorate.